Data storage systems can be incorporated into a wide range of devices, including laptop or desktop computers, tablet computers, digital video recorders, set-top boxes, digital recording devices, digital media players, video gaming devices, video game consoles, cellular telephones, and the like. Magnetic data storage systems include one or more magnetic disks, each comprised of magnetization areas that can be oriented in one of two directions. A magnetic transducer is used to read data from a disk and write data to the disk. Different magnetic recording techniques may be used to store data to the disk. Magnetic recording techniques include, for example, longitudinal magnetic recording (LMR), perpendicular magnetic recording (PMR), and shingled magnetic recording (SMR). Heat assisted magnetic recording (HAMR) may be used with LMR, PMR, or SMR.
Performance of the magnetic transducers (which includes a write head and a read head) varies according to a number of factors. In some cases, the variations result in the part being scrapped, while in other cases the variations can be corrected by modifying circuit parameters of the data storage device. In either case, testing of the magnetic transducers is an important aspect of data storage system performance.
With respect to read head testing, a number of standard measurements are commonly employed to determine the quality of the particular read head being tested. For example, a T50 parameter and a resolution parameter are commonly measured in order to assess read head performance. However, read head nonlinearities and saturation of the read head will distort these parameters. To compensate for read-head nonlinearity, complicated quasistatic transfer curve testing is used, which requires digitizing read-back waveforms and performing complex data processing. The amount of time required performing the test and processing data increases the cost associated with production testing of read heads. It would therefore be beneficial to develop a system and/or method of testing read heads that could be performed quickly.
Read head testing may be performed on a spin stand prior to installation of the read head into a particular data storage device (e.g., hard disk drive). However, in addition to read head testing, similar tests are required once the read head has been installed in a particular application (e.g., hard disk drive) in order to properly space the read head above the magnetic media, which becomes an exercise in determining saturation associated with a read-back signal. This type of testing, although in a different environment, introduces the same type of problems as those experienced in spin stand testing of a read head. It would therefore also be beneficial to develop a system and/or method of testing read head spacing in installed applications that could be performed quickly.